SADE DATABASE UPDATED INFORMATION

OPENING OF ACCESS

D.BLUMSTEIN, P.HENRY, S.LACHERADE CNES-CST DCT/SI/MO

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 2

Calibration Method Using Deserts Sites

Compare two sensors :•

One sensor as reference•

Comparison at TOA level

Reference Sensor

Spectral resampling

Surface reflectance

for sensor 2

Surface reflectance

for reference sensor

Simulated ToA

reflectance for sensor 2

Comparison :

RAk

Sensor 2 MeasurementTOA

SURFACE Needs accounting for:• Atmospheric conditions• Spectral discrepancies• Directional effects

Atmospheric correction to ToA reflectance

Atmospheric correction to surface reflectance

References• GSICS/EP-1, Geneva, Oct 2006 (P.Henry)• GSICS/GRWG-II, Darmstadt, June 2007 (P.Henry)• GSICS/GRWG-III, Camps Spring, Feb 2008 (C.Tinel) Similar geometry of acquisition

(|Δθs|<2,

|Δθv|<2,

|Δφ|<5°)

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 3

SADE Data Base : desert sites

■Content of the SADE data base

NOAA09 / AVHRRNOAA11 / AVHRRNOAA14 / AVHRRNOAA17 / AVHRR3NOAA16 / AVHRR3ADEOS / POLDERADEOS2/ POLDERPARASOLERS2 / ATSR2ERS2 / GOMESeaStar / SeaWIFSSPOT1 / HRV1SPOT2 / HVR2SPOT4 / HRVIR1SPOT4 / VEGETATIONSPOT5 / VEGETATIONSPOT5 / HRSSPOT5 / HRG1ENVISAT/MERISENVISAT/AATSRTERRA / MISRTERRA / MODISAQUA / MODISKOMPSAT-2FORMOSAT-2

1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

AVHRR

POLDER

SPOT

MERIS

MODIS

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 4

Which sensor to use as reference ?

■ Some important criteria to take into accountSpectral coverageGeometry of the viewing (θs, θv)

■ We test here 3 sensors as referenceMODIS (AQUA) : years 2005 and 2007

–

Accessibility

of

data, good

compromize

POLDER (ADEOS): 1996 → 1998–

Multi-directional

capability

MERIS (ENVISAT) : 2002 → 2009–

Best spectral VNIR coverage

■ For intercalibration with AVHRR measurementsAVHRR_LTDR Version 3 (NOAA14): 1995 → 1999 (VERMOTE et al.)

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 5

Spectral coverage of the studied sensors

0

400 500 600 700 800 900 1000

POLD

ERM

ERIS

MO

DIS

AVH

RR

Band not used (saturation on bright targets, absorption, etc.)

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 6

Intercalibration of MERIS (/MODIS et /PARASOL)

MERIS vs PARASOL_POLDER used

as reference

MERIS vs AQUA_MODIS used

as reference

442 nm 753 nm

510 nm 753 nm

RAk

vs

time of MERIS measurement RAk

vs

time of MERIS measurement

RAk

vs

time of MERIS measurement

RAk

vs

time of MERIS measurement

RAk

vs

time of MERIS measurement

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 7

Intercalibration MERIS/MODIS (MODIS as reference)

Bande

412 nm

442 nm

490 nm

510 nm

560 nm

620 nm

665 nm

681 nm

708 nm

753 nm

778 nm

865 nm

885 nm

RAk

avg

1.001

1.003

1.084

1.065

1.027

1.041

0.999

0.993

0.979

1.006

1.009

1.010

1.007

σ

(%)

3.5

3.7

4.1

3.6

2.7

2.3

1.8

1.9

2.3

2.3

2.3

1.9

1.9

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

400 500 600 700 800 900

Wavelength (nm)

delta

(Ak)

MERIS/MODIS

RA k

Good intercalibration

for most of the spectral bands

?

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 8

Intercalibration MODIS/MERIS (MERIS as reference)

Bande

412 nm

443 nm

469 nm

555 nm

645 nm

858 nm

RAk

avg

0.973

0.999

0.928

0.974

0.987

0.991

σ

(%)

3.5

3.7

3.4

2.6

1.9

1.8

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

400 500 600 700 800 900

Wavelength (nm)

delta

(Ak)

MERIS/MODISMODIS/MERIS

Good consistancy

MODIS/MERIS and MERIS/MODIS

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 9

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

400 500 600 700 800 900

Wavelength (nm)

delta

(Ak)

MERIS/MODISMODIS/MERIS

0

400 500 600 700 800 900 1000M

ERIS

MO

DIS

No MODIS band

close to

MERIS bands

490nm and

510nm

No MERIS band

close to

MODIS band

469 nm

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 10

Intercalibration of AVHRR RED band with the 3 studied references

POLDER

MERIS

MODIS

RAk

vs

time of AVHRR (RED band)

RAk

vs

time of AVHRR (RED band)

RAk

vs

time of AVHRR (RED band)

Drift of bias observed with the 3 references (not found with version 2 parameters)exchange of information with E.Vermote in progress

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 11

Intercalibration of AVHRR NIR band with the 3 studied references

POLDER

MERIS

MODIS

RAk

vs

time of AVHRR (NIR band)

RAk

vs

time of AVHRR (NIR band)

RAk

vs

time of AVHRR (NIR band)

Lack of geometry similarity

NOAA14 orbit drift

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 12

Intercalibration of GEO sensors

0

50

100

400 450 500 550 600 650 700 750 800 850 900 950 1000

ME

RIS

MO

DIS

GO

ES

MS

G

Wavelength

(nm)

Note : Interest of MODIS SWIR band (no such band on MERIS)Interest of MERIS for MSG NIR band

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 13

MODIS ? MERIS ? As reference

■ Both sensors are very close in terms of intercalibration

■ Both sensors provide similar results when used as reference

■ Interest of MERIS higher spectral sampling usable on desert sites

■ Interest of SWIR MODIS band

■ Availability of MERIS measurements In CNES SADE database 20 desert sitesOther sites : ocean, sun glint

■ CNES uses both sensors

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 14

Opening the SADE database (I)■ References to previous presentations

GSICS/EP-1, Geneva, Oct 2006 (P.Henry)GSICS/GRWG-II, Darmstadt, June 2007 (P.Henry)GSICS/GRWG-III, Camps Spring, Feb 2008 (C.Tinel)

■ Database content : 3 levels Measurements (Visible and NIR)•

Sensors : Polder1, Polder2, Parasol, SPOTs, SeaWiFS, VEGETATION 1&2, AVHRR, MERIS, MODIS, ...

•

Targets : Deserts, Ocean, Sun Glint, Clouds (DCC) and Snowy sites•

Associated Meteo

Data Elementary Calibration ResultsVicarious Calibration Results

■Only desert measurements are used for intercalibrationCNES proposes to provide access to desert data to GSICS members via WEB interfaceSimple data format (ASCII, to be discussed)

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 15

Opening the SADE database (II)

■Export measurements available on Desert sites (possibly Dôme-C)■Existing SADE export format

Field Name UnitArea size —Latitude degLongitude degSolar azimuth angle degSolar Zenith angle degWater Vapour content g.cm-2Ozone content cm.atmSurface Pressure mbarSurface Wind Speed m.s-1AerosolsNO2CHP1CHP2Date/time of the measurementProduct Reference

commonto all

bands

Field Name UnitBand IdMeasurement IdMeasurement value = averageMeasurement std.dev.Viewing azimuth angle degViewing Zenith angle degBand IdMeasurement IdMeasurement value = averageMeasurement std.dev.Viewing azimuth angle degViewing Zenith angle degBand IdMeasurement IdMeasurement value = averageMeasurement std.dev.Viewing azimuth angle degViewing Zenith angle deg

…

Band 1

Band 2

+ Bands Characteristics

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 16

Opening the SADE database (III)

■

Two major options1. Provide data based upon user request (web site interface)

■

Selection by user : Sensor, Site, Period, …■

SADE database Request done by CNES■

Data made available on a server for a limited period of time2. Put data systematically on a server

■

Hierarchical organization of the files : Sensor / Year / Site■

Other organization of data that better suits GSICS member needs ?■

Updated every 6 months (TBC)

■

Choice will depend on ■

Frequency of export requests■

Typology of the requests (1 or many sensors ?, 1 or many sites ?, …)

■

GSICS members feedback would be helpful to make the correct choice (today the option 2 is the preferred one for CNES)

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 17

SADE database capability extension

■ It is very easy to add a new sensor in the databaseDone recently for THEOS satelliteMeasurements provided in the format described earlierCould be used for GEO satellites without any modification

■ Other deserts sites can also be easily addedFor example, DOME-C sites where introduced recently

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 18

BACKUP SLIDES

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 19

■

DefinitionsOptical sensors are calibrated against reflectance

•

k: Spectral band•

DN : Digital Number (Meris Level 0, corrected for instrumental defects)•

ρ

: Reflectance•

Ak

: Sensitivity of instrument for spectral band k

Calibration results are expressed this way

(Method)ρρ

=AA

=RApredictedk,

1)measured(Lk,

L1k,

methodk,k

)(θρA=DN skkk .cos.

Calibration of opical sensors using natural targets

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 20

Libya 1 site – 565 nm band (Snyder model)

P0

P90

P45

θs = 40°

P0

P45

P90

BRDF Study of desert sites

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 21

1 2 3 4 5 67 8 9 10 11 1213 14 15 16 17 1819 20 21 22 23 2425 26 27 28 29 3031 32 33 34 35 36

Extraction of a 720*720 km2

area centred on Dome C base

divided in 36 smaller areas (120*120 km2)

each zone carefully studied against different parameters

Dôme C characterization using VGT images

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 22

4 zones (120*120 km2)

finally selected : Dome 1,2,3 & C

large zone (480*360 km2)

more suitable for calibration

Calibration over different zones allows to distinguish sensor behaviour from site behaviour

Choice of 4 calibration sites

GSICS – GRWG-IV Meeting, JMA Tokyo, January 28-30, 2009 23

PO

LDE

RM

ER

ISM

OD

IS